1. Field of the Invention
The present invention generally relates to a back light module of a liquid crystal display, and more particularly, to a back light module of a liquid crystal display (LCD) which is provided with a sliding groove for mounting the optical films therein.
2. Description of the Related Art
Due to the advance of electronic technology, especially for the popularity of portable electronic products, the requirements of light, compact and low-energy consuming display are gradually increasing. With the advantages of low-energy consuming, low-heat dissipation, light weight and non-luminescence display, liquid crystal displays (LCD) have been widely used in the electronic products and even have replaced the traditional CRT displays.
Referring to FIG. 1, it depicts a conventional liquid crystal display (LCD). In general, the liquid crystal display includes a liquid crystal panel 10 which has two substrates with liquid crystal material sealed therebetween, a back light module 20 of the direct type disposed under the liquid crystal display panel 10, and a case 11.
The back light module 20 of the direct type is utilized to distribute the light transmitted from a light source uniformly over the surface of the liquid crystal display panel 10. For the liquid crystal display in large dimensions, the back light module of the direct type is widely used because of its easy installation and its low cost.
The back light module 20 of the direct type includes a housing 70 which has a reflective sheet 60 disposed on the bottom surface of the housing 70, lamps 50, such as a fluorescence cathode tube, disposed at the bottom of the housing 70, a plurality of optical films 30, such as a diffuser sheet and a prism sheet, disposed on the upper surface of the housing 70, and a diffuser plate 32 disposed between the optical films 30 and the housing 70. The lamps 50 are spaced apart from each other and disposed within the display area of the liquid crystal panel 10. Since the light source, i.e. the lamps 50, is a linear light source, the lamps 50 cannot provide light evenly illuminating the liquid crystal panel 10. Therefore, the diffuser plate 32 and the optical films 30 such as a diffuser sheet and a prism sheet have to be disposed between the lamps 50 and the liquid crystal panel 10 to provide a panel light source device with uniform luminance.
Many back light modules have been disclosed in the prior art, such as those disclosed in U.S. Pat. No. 6,407,781 B2 issued to Kitada on Jun. 18, 2002 and in U.S. Pat. No. 6,417,833 B1 issued to Takemoto et al. on Jul. 9, 2002, which are all incorporated herein by reference.
The back light module 20 is normally provided with a front frame 40 disposed in front of the back light module 20. The front frame 40 is usually made of aluminum, stainless steel, or zinc-plated steel for fixing the optical films 30 and the diffuser plate 32 on the back light module 20, and the housing 70 is used for supporting the liquid crystal panel 10 and the back light module 20. For the liquid crystal display with large dimensions, especially for the liquid crystal display larger than 30 inches, the front frame 40 cannot be formed by a punching process and thus must be formed by a welding process, wherein the welding process is time-consuming and expensive.
Accordingly, there exists a need for a liquid crystal display having a direct type back light module without the metal frame.